Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756494AbXJJPF1 (ORCPT ); Wed, 10 Oct 2007 11:05:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754341AbXJJPFU (ORCPT ); Wed, 10 Oct 2007 11:05:20 -0400 Received: from smtp2.linux-foundation.org ([207.189.120.14]:41428 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755155AbXJJPFS (ORCPT ); Wed, 10 Oct 2007 11:05:18 -0400 Date: Wed, 10 Oct 2007 08:04:29 -0700 (PDT) From: Linus Torvalds To: Nick Piggin cc: Hugh Dickins , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: remove zero_page (was Re: -mm merge plans for 2.6.24) In-Reply-To: <200710100030.28806.nickpiggin@yahoo.com.au> Message-ID: References: <20071001142222.fcaa8d57.akpm@linux-foundation.org> <200710100030.28806.nickpiggin@yahoo.com.au> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1387 Lines: 37 On Wed, 10 Oct 2007, Nick Piggin wrote: > > It just seems like now might be a good time to just _try_ removing > the zero page Yes. Let's do your patch immediately after the x86 merge, and just see if anybody screams. It might take a while, because I certainly agree that whoever would be affected by it is likely to be unusual. > OK, maybe this is where we are not on the same page. > There are 2 issues really. Firstly, performance problem of > refcounting the zero-page -- we've established that it causes > this livelock and that we should stop refcounting it, right? Yes, I do agree that refcounting is problematic. > Second issue is the performance difference between removing the > zero page completely, and de-refcounting it (it's obviously > incorrect to argue for zero page removal for performance reasons > if the performance improvement is simply coming from avoiding > the refcounting). Well, even if it's a "when you don't get into the bad behaviour, performance difference is not measurable", and give a before-and-after number for some random but interesting load. Even if it's just a kernel compile.. Linus - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/